1. Field of the Invention
The present invention relates to a thin film transistor (TFT) array substrate, and more particularly to a TFT array substrate and repairing methods thereof.
2. Description of the Related Art
With the advance of semiconductor and display technology, Cathode Ray Tube (CRT) had been dominating the market for a long time due to its good display quality and low costs. Due to the change of users' behavior with respect to the multi-terminals or multi-displays and the concern of power consumption, CRT may not provide desired demands. Accordingly, Thin Film Transistor Liquid Crystal Display (TFT-LCD) with high display quality, space-efficiency, low power consumption and non-radiation has been gradually replacing CRT in the market.
TFT-LCD usually comprises a thin film transistor array substrate, a color filter array substrate and a liquid crystal layer. The thin film transistor array substrate comprises a plurality of thin film transistors arranged in an array, and pixel electrodes corresponding thereto. The thin film transistors serve as switches of pixel units. In order to control the pixel units individually, scan lines and data lines are used to select a specified pixel so as to provide the operating voltages to the pixel and display the data corresponding to the pixel. A portion area of the pixel electrode covers the scan line or the common line so as to form a storage capacitor. The storage capacitor includes, for example, a first-metal/insulator/second-metal (MIM) storage capacitor and a first-metal/insulator/indium-tin-oxide (MII) storage capacitor. Following are the detailed descriptions of these storage capacitors.
FIG. 1 is a schematic cross sectional view showing a prior art MIM storage capacitor. Referring to FIG. 1, the MIM storage capacitor Cst is formed by the scan line or the data line 100 and the capacitor electrode 120. In the MIM capacitor, the scan line or the data line 100 is isolated from the capacitor electrode 120 by the gate insulator 110. The capacitance of the storage capacitor Cst relates to the thickness of the gate insulator 110. The pixel electrode 140 is coupled to the capacitor electrode 120 through the contact 132 in the passivation layer 130.
FIG. 2 is a schematic cross sectional view showing a prior art MII storage capacitor. Referring to FIG. 2, the MII storage capacitor is formed by the scan line or the data line 200 and the pixel electrode 230. Compared with the MIM storage capacitor, the scan line or the data line 200 of the MII storage capacitor is isolated from the pixel electrode 230 by the gate insulator 210 and the passivation layer 220. The capacitance of the storage capacitor Cst relates to the thickness of the gate insulator 210 and the passivation layer 220.
Either the MIM storage capacitor or the MII storage capacitor is used in the pixels of TFT-LCD so as to store charges. However, defects or particles resulting from processes may exist in the dielectric layer, i.e. the gate insulator or the passivation layer, so as to cause the leakage issue of the storage capacitor. Moreover, un-opened contact holes or pixel electrode residues may fail the storage capacitor. This makes abnormal operation of the pixel and decreases the display quality.